A conventional vital capacity examining device generally includes a blowing tube unit which is cooperated with a rotatable member with multiple blades which are driven by the blowing via the blowing tube unit. An electronic circuit detects the revolutions of the blades and determines the vital capacity of the user. However, the device has to be externally and electrically connected with batteries or electric power so as to keep the device to be functioned normally. The transmission of the result of the records is limited by the length of the electric cables that are connected with the device. The conventional vital capacity examining device involves too many parts, consumes electric energy, has high manufacturing cost, is easily broken and affects the preciseness of the result.